This invention relates to a method for separating certain constituents from carbonaceous fluids. More paticularly, this invention relates to a method for separating certain catalyst poisoning impurities, contaminants and/or environmental pollutants from carbonaceous fluids.
Heretofore, several processes for separating catalyst poisoning impurities, contaminants and/or environmental pollutants such as arsenic, selenium, and the like, from carbonaceous fluids have been proposed. In general, the prior art processes involve passing of the carbonaceous fluid through a fixed bed of material that will remove the catalyst poisoning impurity, contaminant and/or environmental pollutants either by absorption thereof onto a solid or by reaction therewith. Materials which will react with catalyst poisoning impurities, contaminants and/or environmental pollutants such as arsenic and selenium include the oxides and sulfides of various metals, particularly the iron group metals such as iron, nickel and cobalt. The metal oxides and metal sulfides may comprise the entire fixed bed or the same may be incorporated with a suitable carrier or support. Suitable carrier materials known in the prior art include silica, alumina, magnesia, zirconia, thoria, zinc oxide, chromium oxide, silicon carbide, naturally occurring carriers such as the clays, including special clays like fuller's earth, kieselguhr, pumice, bauxite and the like. A combination of two or more carriers may, of course, be used.
As is believed well known in the prior art, some of these carriers will act as absorbents for the catalyst poisoning impurities, contaminants and/or environmental pollutants. When the metal oxide and/or metal sulfide is, then, used in combination with such a carrier, the catalyst poisoning impurities, contaminants and/or environmental pollutants will be separated both by reaction with the metal oxide and/or metal sulfide and by absorption on the carrier. Moreover, and as indicated in U.S. Pat. No. 3,954,603 which issued on May 4, 1976, it is possible that the metal oxide and/or metal sulfide act as an absorbent.
While the prior art processes have, generally, been reasonably effective in separating arsenic and selenium from carbonaceous fluids containing the same, care must be exercised to prevent a breakthrough of catalyst poisoning impurities, contaminants and/or environmental pollutants when the bed has reached its reactive and/or absorbent limit. In such operations, then, continuous operations require a plurality of fixed beds and the spent beds must be replaced since they are not generally subject to regeneration. Moreover, the prior art processes are not particularly effective for processing shale oils and similar hydrocarbon liquids which may contain significant concentrations of fines due to irreversible plugging of the beds as a result of the fines content before the fixed bed has separated its optimum or maximum amount of catalyst poisoning impurities, contaminants and/or environmental pollutants. The need, then for an improved process for separating such catalyst poisoning impurities, contaminants and/or environmental polluntants which does not require bed replacement and which is not subject to plugging by fines or other impurities that may be contained in the carbonaceous fluid is believed readily apparent.